Bad "stair-steeping" in high-contract captures

Discussion in 'Archived Threads 2001-2004' started by John_Berger, Aug 25, 2002.

  1. John_Berger

    John_Berger Cinematographer

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    Paging Dr. Kleist! Dr. Kleist! [​IMG]
    Just wondering if anyone has seen this.
    When capturing from my DV camcorder (over S-Video directly to MPEG-2 because DV AVI files suck and take up way, WAY too much space), I get severe stair-stepping only in those contiguous areas of the screen with high contrast, such as a spotlight on a person wearing a bright shirt standing against a black backdrop. Yet in the same frame contiguous areas of low contrast, like the face, or scenes with full background lighting come out just fine with no stair stepping except when it is a direct result of resolution.
    I'm not sure why the MPEG-2 software (which I'm assuming is the cuplrit) is so sensitive to these high-contrast areas, and to the discerning eye, like mine, this stair-stepping is distracting.
    Are there compression settings that can be changed during the capture and/or rendering to remove these issues, assuming that my video capture driver supports changing such parameters?
    I have already started looking into purchasing polzrized and UV lenses for my camcorder, so I'm comfortable that they will remove much of the spotlight "wash out" effect. But this is one of those things where the scientific computer geek in me is saying, "What's up wit dat?!" [​IMG]
    Dr. Kleist! Second page for Dr. Kleist! [​IMG]
     
  2. John_Berger

    John_Berger Cinematographer

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    It would also help if I would learn how to proof-read the subject of my thread before I submit it. "Stiar-steeping"?? "Contract"?? [​IMG] MODERATORS!!!! Vince! Patrick!
    I need caffeine. [​IMG]
     
  3. Mark Hsieh

    Mark Hsieh Agent

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    Well one reason may be the resolution you're capturing at. If its a relatively high, try turning it down.

    I've never had a problem with a direct DV transfer, it's always looked better if not the same, as my s-video transfer. After it captures, I just reconvert it back to a divx format and the file size just goes down alot.
     
  4. TedD

    TedD Supporting Actor

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    Get a bigger HD, because you are throwing away the entire reason for DV by not using firewire.

    You are compressing the signal, than decompressing it, then compressing it again. If you want the best quality, you need to perform edits etc. in the DV realm, then render direct to MPEG2. BTW, there is a tremendous difference in the quality of the different compression packages out there. TMPGenc is one of the best, as a reasonable cost.

    The only way to achieve the highest quality MPEG's with reasonable file sizes is with 2 pass VBR compression, which can't be done in real time.

    Therefore you have to have a non-real time input to the MPEG2 compression process.

    You also have to have the fields processed in the correct order, make sure you have the "Lower field first" option selected.

    There are tons of Web sites out there with endless discussion on the topic of MPEG2 compression.

    Do a Google search.

    Ted
     
  5. Jeff Kleist

    Jeff Kleist Executive Producer

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    yep, your culprit is probably the direct MPEG-2 capture

    Go firewire. You can pick up a 120GB drive for around $100 on pricewatch. Don't cheap out on your firewire card either, get a Pinnacle or Canopus
     
  6. John_Berger

    John_Berger Cinematographer

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  7. Wayne Bundrick

    Wayne Bundrick Cinematographer

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    Would the Microsoft DV codec be involved in a firewire transfer? I'd think it would introduce problems only if you encode video using Microsoft DV. But in this case, your camera has already done the encoding.
    Unless the Microsoft codec has a decoding bug, which is unexcuseable. Every codec should decode the exact same output, to within an occasional rounding error in the least significant bit during the inverse discrete cosine transform stage. If it doesn't then by definition it is defective. But there is no standard for encoding, all that is required is that it outputs a compliant bitstream, and a bitstream could be compliant but full of garbage.
    The stairstepping problem could be caused by the camera, there's an article at http://www.dvcentral.org/DV-Beta.html which describes the same artifact. Are you able to capture video from the camera in a way that does not have stairstepping? If you can then it's not the camera.
     
  8. Jeff Kleist

    Jeff Kleist Executive Producer

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    Wayne, it would be involved in any rendering that was done.

    The MS codec introduces marked artifacting and detal loss that other codecs do not. It's highly inferior to the Canopus/Pinnacle codecs
     
  9. John_Berger

    John_Berger Cinematographer

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  10. Jeff Kleist

    Jeff Kleist Executive Producer

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    They are only for use with their hardware
     
  11. Wayne Bundrick

    Wayne Bundrick Cinematographer

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    You can buy the Canopus codec as software-only (well, software-only except for the copy protection dongle), it's part of the DV Booster Pack and it's $249 MSRP, or about $199 street.
     
  12. John_Berger

    John_Berger Cinematographer

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  13. Jeff Kleist

    Jeff Kleist Executive Producer

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    There are a few, I forget what they are. None of them measure up to the quality of those 2 codecs tho

    I did a test on color bars, I had to re-render it _5_ times to be able to pick up any noticeable degredation.
     

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